Frémy's salt is achemical compound with the formula (K4[ON(SO3)2]2), sometimes written as (K2[NO(SO3)2]). It is a bright yellowish-brown solid, but its aqueous solutions are bright violet.[1][2] The related sodium salt,disodium nitrosodisulfonate (NDS, Na2ON(SO3)2,CAS 29554-37-8) is also referred to as Frémy's salt.[3]
Regardless of the cations, the salts are distinctive because aqueous solutions contain the radical [ON(SO3)2]2−.
Frémy's salt, being a long-lived free radical, is used as a standard inelectron paramagnetic resonance (EPR) spectroscopy, e.g. for quantitation of radicals. Its intense EPR spectrum is dominated by three lines of equal intensity with a spacing of about 13 G (1.3 mT).[4][5][6]
It has been used in some oxidation reactions, such as for oxidation of some anilines and phenols[7][8][9][10][11] allowing polymerization and cross-linking of peptides and peptide-basedhydrogels.[12][13]
It can also be used as a model for peroxyl radicals in studies that examine the antioxidant mechanism of action in a wide range of natural products.[14]
Frémy's salt was discovered in 1845 byEdmond Frémy (1814–1894).[15] Its use in organic synthesis was popularized byHans Teuber, such that an oxidation using this salt is called theTeuber reaction.[9][10]
^abWehrli PA, Pigott F (1972). "Oxidation with the nitrosodisulfonate radical. I. Preparation and use of sodium nitrosodisulfonate: trimethyl-p-benzoquinone".Organic Syntheses.52: 83.doi:10.15227/orgsyn.052.0083.
^Wertz JE, Bolton JR (1972).Electron Spin Resonance: Elementary Theory and Practical Applications. New York: McGraw-Hill.ISBN978-0-07-069454-5. See page 463 for information on intensity measurements and page 86 for an EPR spectrum of Frémy's salt.
^Colacicchi S, Carnicelli V, Gualtieri G, Di Giulio A (2000). "EPR study of Frémy's salt nitroxide reduction by ascorbic acid; influence of bulk pH values".Res. Chem. Intermed.26 (9):885–896.doi:10.1163/156856700X00372.S2CID98775951.
^Zielonka J, Zhao H, Xu Y, Kalyanaraman B (October 2005). "Mechanistic similarities between oxidation of hydroethidine by Frémy's salt and superoxide: stopped-flow optical and EPR studies".Free Radical Biology & Medicine.39 (7):853–863.doi:10.1016/j.freeradbiomed.2005.05.001.PMID16140206.
^Islam I, Skibo EB, Dorr RT, Alberts DS (October 1991). "Structure-activity studies of antitumor agents based on pyrrolo[1,2-a]benzimidazoles: new reductive alkylating DNA cleaving agents".Journal of Medicinal Chemistry.34 (10):2954–2961.doi:10.1021/jm00114a003.PMID1920349.
^Xue W, Warshawsky D, Rance M, Jayasimhulu K (2002). "A metabolic activation mechanism of 7H-dibenzo[c,g]carbozole viao-quinone. Part 1: synthesis of 7H-dibenzo[c,g]carbozole-3,4-dione and reactions with nucleophiles".Polycyclic Aromatic Compounds.22 (3–4):295–300.doi:10.1080/10406630290026957.S2CID95507636.
^Wilchek M, Miron T (March 2015). "Mussel-inspired new approach for polymerization and cross-linking of peptides and proteins containing tyrosines by Frémy's salt oxidation".Bioconjugate Chemistry.26 (3):502–510.doi:10.1021/bc5006152.PMID25692389.
^Liu ZL, Han ZX, Chen P, Liu YC (November 1990). "Stopped-flow ESR study on the reactivity of vitamin E, vitamin C and its lipophilic derivatives towards Frémy's salt in micellar systems".Chemistry and Physics of Lipids.56 (1):73–80.doi:10.1016/0009-3084(90)90090-E.PMID1965427.
